As a color image forming apparatus, there has conventionally been known an apparatus including four pairs of photoconductor drums and rollers which are in pressure contact with the photoconductor drums (hereinafter referred to as “pairs of transfer rollers”), the pairs of transfer rollers being aligned on one row at intervals, in which recording media (hereinafter referred to as “sheets”) are conveyed sequentially through nip sections of the respective pairs of transfer rollers, and toner images formed on the photoconductor drum surfaces with electrophotographic method are sequentially transferred onto the sheets (see, e.g., JP H07-319254 A).